Load a portion of UI from a plugin QML (dynamic GUI) and expose C++ models to it

[gmanish]

You could register a QML singleton type using a plugin specific namespace and then let the QML code "instantiate" the model.

Cheers,
_

Thanks for your time on this. Do you mean using qmlRegisterType<X>("com.mycompany.X", 1, 0, "X")?

[anda_skoa]

I meant qmlRegisterSingletonType()

However, there might be another option that is closer to what you tried.
I assume you are using QQmlComponent to create the UI. You can pass a context to its create method.
E.g. something like this (not tested)

QQmlContext *pluginContext = new QQmlContext(view.engine());
pluginContext->setContextProperty("model", plugin->getModel());
 
QQmlComponent component(view.engine(), plugin->getQMLPath());
component.create(pluginContext);

QQmlContext *pluginContext = new QQmlContext(view.engine());
pluginContext->setContextProperty("model", plugin->getModel());

QQmlComponent component(view.engine(), plugin->getQMLPath());
component.create(pluginContext);

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Cheers,
_

[gmanish]

I meant qmlRegisterSingletonType()
However, there might be another option that is closer to what you tried.
I assume you are using QQmlComponent to create the UI. You can pass a context to its create method.
_

I'm using the following to create the main UI (i.e. loading main.qml). It is in this view that I want to load the plugins QML components:

QGuiApplication app(argc, argv);
QQuickView viewer;
 
viewer.setSource(QUrl("qrc:///..."));
viewer.showExpanded();
return app.exec();

QGuiApplication app(argc, argv);
QQuickView viewer;
 
viewer.setSource(QUrl("qrc:///..."));
viewer.showExpanded();
return app.exec();

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Also, I found this thread that seems pertinent to my problem. However, I cannot fully comprehend it. Specifically, what are window1, window2 & window3 in the given solution.

How do I create my main UI using QQmlComponent and later add the QQmlComponent created using the method you specify to the main UI's QQmlComponent? I found a possible implementation here. But when I run it, I get a crash because:

QQuickWindow *window = qobject_cast<QQuickWindow *>(topLevel);

QQuickWindow *window = qobject_cast<QQuickWindow *>(topLevel);

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evaluates to window = NULL

[anda_skoa]

QQuickWindow *window = qobject_cast<QQuickWindow *>(topLevel);

QQuickWindow *window = qobject_cast<QQuickWindow *>(topLevel);

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evaluates to window = NULL

Is your top level item a Window element? If not, cast it to whatever you are using, e.g. QQuickItem

Cheers,
_

[gmanish]

Mostly for future visitors, I did manage to get this working. Following is a tiny code fragment that highlights the solution:

QQmlContext*        pluginContext = new QQmlContext(mView->engine());
        QmlComponent*     component(new QQmlComponent(mView->engine(), "/PATH/TO/QML.qml"));
        QObject*               compRoot = NULL;
 
        pluginContext->setContextProperty("model", myModelObject);
        compRoot = component->create(pluginContext);
        if (component->isReady()) {
            QQuickItem* item = qobject_cast<QQuickItem*>(compRoot);
            QPointF     point(posHelper.getLeft(), posHelper.getTop());
            QSizeF      size(posHelper.getWidth(), posHelper.getHeight());
 
            item->setParentItem(mRoot); // The item pointer obtained through QQuickView.rootObject
            item->setPosition(point);
            item->setSize(size);
 
            qDebug() << "Card (" << posHelper.getCurRow() << ", " << posHelper.getCurCol() << "): " <<
                            "(" << point.x() << ", " << point.y() << ") - " <<
                            "(" << size.width() << ", " << size.height() << ")";
            return component;
        } else {
            qWarning() << "Failed to create component from C++:" << component->errorString();
        }
    }

QQmlContext*        pluginContext = new QQmlContext(mView->engine());
        QmlComponent*     component(new QQmlComponent(mView->engine(), "/PATH/TO/QML.qml"));
        QObject*               compRoot = NULL;

        pluginContext->setContextProperty("model", myModelObject);
        compRoot = component->create(pluginContext);
        if (component->isReady()) {
            QQuickItem* item = qobject_cast<QQuickItem*>(compRoot);
            QPointF     point(posHelper.getLeft(), posHelper.getTop());
            QSizeF      size(posHelper.getWidth(), posHelper.getHeight());

            item->setParentItem(mRoot); // The item pointer obtained through QQuickView.rootObject
            item->setPosition(point);
            item->setSize(size);

            qDebug() << "Card (" << posHelper.getCurRow() << ", " << posHelper.getCurCol() << "): " <<
                            "(" << point.x() << ", " << point.y() << ") - " <<
                            "(" << size.width() << ", " << size.height() << ")";
            return component;
        } else {
            qWarning() << "Failed to create component from C++:" << component->errorString();
        }
    }

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The thing that did the trick was:

item->setParentItem(mRoot)

item->setParentItem(mRoot)

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